PRIMITIVE NEUROECTODERMAL TUMOR OF THE KIDNEY - ANOTHER ENIGMA - A PATHOLOGICAL, IMMUNOHISTOCHEMICAL, AND MOLECULAR DIAGNOSTIC STUDY

Primitive neuroectodermal tumor (PNET), the second most common type of sarcoma in the first two decades of life, rarely presents as an organ -based neoplasm. Rather, it is seen typically in the soft tissues of t he chest wall and paraspinal region. We report a case of primary PNET of the kidney in a 17-year-old girl who presented with abdominal pain, hematuria, and an abdominal mass. Nodules and sheets of monotonous-ap pearing primitive round cells and the formation of rosettes focally we re the principal microscopic features. The tumor cells were uniformly immunoreactive for vimentin, cytokeratin, neuron-specific enolase, and 013 (CD99). In addition, the characteristic translocation of PNET and Ewing sarcoma, t(11;22)(q24;q12), was detected by polymerase chain re action (PCR). Eight previous examples of renal PNET have been reported in the literature in the past 2 years, but only three of these cases have had complete immunohistochemical evaluation with the demonstratio n of 013 positivity. To our knowledge the present case is the only one to date demonstrating the recurrent translocation t(11;22)(q24;q12) b y PCR. Assuming that the previous cases in the literature are bona fid e examples of PNET. the kidney may be another site of predilection for this usual soft-tissue neoplasm. We are once again confronted with th e dilemma about the nature of the progenitor cell.